Pioneered by A. H. Zewail, nuclear motion in biomolecules as well as the formation and rupture of chemical bonds have been accessed extensively by femtosecond pump-probe spectroscopy. However, the resolution offered by femtosecond spectroscopy is insufficient to track the dynamics of electronic motion in atoms or molecules since they evolve on an attosecond to few-fs time scale and thus remain elusive so far.

In this talk, I will introduce the concept of 1,2streaking spectroscopy as a pump-probe spectroscopic technique to investigate electron correlations with attosecond resolution. I will also discuss the generation of attosecond extreme ultraviolet (XUV) pulses using 3high harmonic generation (HHG). Finally, I will briefly explain the recent studies on 4breakdown of single active-electron approximation in photoelectron emission by recording up to few attosecond retardation of the dislodged photoelectron due to electronic correlations.

Currently, more than 60% of the energy produced from fossil fuels is lost as waste heat. Thermoelectric energy conversion, which is the process of converting
thermal energy to electricity, without hazardous emissions, is attracting attention as a potential energy harvesting technology. The energy conversion efficiency
of thermoelectric materials is determined by the dimensionless figure of merit (ZT), which is defined as ZT = T, where ‘S’ is the Seebeck coefficient, ‘σ’ is the
electrical conductivity, ‘κ’ is the thermal conductivity and ‘T’ is the absolute temperature. Maximizing ZT is the primary objective of research in
thermoelectrics. However, the parameters, S, σ and κ cannot, in general, be varied independently to maximize ZT.

In this talk, I will introduce elements of thermoelectricity and discuss on potential approaches to enhance ZT. I will discuss on nanoscience based approaches to
increase the Seebeck Coefficient, S, while not significantly decreasing electrical conductivity, σ. I will also present on the possible approaches to decrease
lattice thermal conductivity while not significantly decreasing electrical conductivity. Finally, I will also touch upon quantum mechanics based approaches
utilizing band engineering and nano-structuring that could lead to enhanced thermoelectric energy conversion efficiency.

Unlocking the Potential of Metal Fluorides for Electrochemical Energy Storage

Date & Time : Friday 15th February 2019 at 11:00 AM
Venue : SSCU Auditorium
Abstract:
Fluorine has outstanding potential as an electrode due to its high electronegativity and comparably lightweight. Employing fluorine in elemental form as a component of electrode material (in contrast to Li) is difficult, however, due to its high chemical reactivity and gaseous state. Instead, the fluoride anion (F-) may be utilized as an electrochemically stable transport ion between two electrodes. By choosing an appropriate metal/metal fluoride system combined with suitable fluoride transporting electrolyte, novel electrochemical cells can be built. Indeed, primary electrochemical cells based on fluoride transfer were realized four decades back [1], but largely overlooked until the demonstration of rechargeable fluoride ion batteries (FIBs) [2]. Since the demonstration of rechargeable FIBs, we are working on various aspects related to FIBs with the aim of developing sustainable fluoride ion batteries [3-6]. So far rechargeable FIBs have been demonstrated only at an elevated temperature like 150 °C and above. Recently, for the first time, we have demonstrated room-temperature (RT) rechargeable fluoride-ion batteries using BaSnF4 as fluoride transporting solid electrolyte [7]. BaSnF4 exhibits high ionic conductivity of 3.5×10-4 S cm-1 at RT but limited by low electrochemical stability window. In contrast tysonite-type, La0.9B0.1F2.9 electrolyte shows a large electrochemical stability window, but it has the drawback of lower ionic conductivity at RT (0.4×10−6 S cm−1). To overcome these limitations of the low electrolyte stability of BaSnF4 and low ionic conductivity of La0.9B0.1F2.9, we developed an interlayer electrolyte. Pressing a thin layer of La0.9Ba0.1F2.9 together with BaSnF4 enhanced the total conductivity of the pellet (compared to pure La0.9Ba0.1F2.9) while it physically isolated the less stable and highly conductive electrolyte (BaSnF4) from the anode (Ce). This approach allowed the demonstration of relatively high voltage FIBs at RT which otherwise inoperable either with BaSnF4 or La0.9Ba0.1F2.9 electrolyte alone [8]. Apart from applications in FIBs, transition metal fluorides could be used as high capacity cathode materials for lithium-ion batteries (LIBs), due to their ability to reversibly react with Li at relatively high potentials. However, metal fluorides are electrical insulators, exhibiting slow reaction kinetics. Consequently, efficient synthesis of metal fluoride-carbon nanocomposites is crucial to get adequate electrochemical performance. We have developed a new and facile one-step method for the chemical synthesis of novel carbon-metal fluoride nanocomposites and established their feasibility as cathode materials for LIBs [9-10]. For sodiumion batteries (SIBs) we propose weberite-type sodium metal fluorides (SMF), a new class of high voltage and high energy density materials which are so far unexplored as cathode materials for SIBs [11]. Weberite-type SMF is the only class of compounds that can offer high energy density than the state-of-the-art LIB cathodes. More than 70 compounds with Na2MM’F7 composition adopts the weberite-type structure, which demonstrates the high stability of the structure. We have modeled 22 known and 10 new compounds. Apart from the high energy density, the weberite-type structure shows low Na diffusion barriers with pseudo-3D diffusion paths. The high energy density combined with low diffusion barriers for Na makes this type of compounds promising as cathode materials for SIBs. Also, we found few lithium metal fluorides serve as excellent solid Li+ conducting electrolytes for solid-state lithium batteries, overcoming the short comes of ceramic and sulphide based solid electrolytes [12]. Overall, the presentation will highlight the potential of metal fluorides in electrochemical energy storage systems.

SEMINAR
Speaker: Mr. Debasish Mondal
Title: “An Introduction to Quantum Computing”
Date & Time: February 14, 2019 at 4.00 p.m
Venue: SSCU AUDITORIUM
Abstract:
The invention of the classical computer transformed human development. Today’s classical computers are capable of solving the most complex of problems and could
even challenge humans in games such as Go and Chess. However, these best of class classical computers use orders of magnitude larger power when compared to a
human brain, which is estimated to use about 20 W of power. Quantum computing as a computational approach was proposed to be more efficient than classical
computing, especially for complex computational tasks. In this talk, I will discuss the fundamental differences between classical and quantum computing; and
introduce quantum logic gates while contrasting them with classical gates. I will also discuss the approaches for building quantum circuits and outline the steps
for performing logic operations using quantum circuits. Thereafter, I will discuss the implementation of two important quantum algorithms: the Grover’s algorithm
and the Shor’s algorithm and reason out the necessity for quantum-computing approaches for solving such complex tasks. Finally, I will touch upon the
difficulties in building a physical quantum computer and briefly mention the recent progress in this field.

Rechargeable batteries are the unavoidable objects in our modern life style. Their extensive applications in portable electronics lead the primary focus of R&D to Lithium-ion batteries (LIBs) within the past few decades. In recent years, new aspects like electric vehicles (EVs) and stationary grid storages are demanding for new materials with high power and energy densities. Though LIBs have many promising features, there are issues related to resource of lithium and other LIB components. If the EVs and grid storage reach the global market it will increase the materials demand and supply chain will be challenged. Sodium can be a better substitute for lithium which poses similar chemical properties. Today researchers motivated towards sodium ion batteries (SIBs) because of large abundancy and the hope to make a battery cheaper than LIBs.

In this talk, I will discuss the comparison of selected electrode materials when used in LIBs and SIBs. The comparison will mainly be focused on the structural behavior of intercalation materials during the charge/discharge cycles, advantages and challenges on conversion electrodes will be addressed.

Modern day science and technology involves study of crystalline materials with defects and disorders as well as non-crystalline materials in lieu of perfect crystalline materials. Completely different approaches from routine crystallographic methods are needed to determinethe 3D atomic arrangement of these materials. Transmission electron microscopy (TEM) uses two-dimensional (2D) projection images to produce images of crystal defects and dislocations at atomic resolution, however it does not fully represent the underlying 3D structures. The need to obtain higher dimensionality ‘structures’ using lower dimensionality data in different fields of physical and life sciences is necessitated by the advances made by electron tomography techniques in recent years. In this talk, I will discuss various 3D image reconstruction methods and the issues associated with electron tomography. The achievement of atomic resolution inthe 3D structure reconstruction of functional materials will also be addressed.

Date & Time : Monday 21st January 2019 at 11:00 AM
Venue : SSCU Auditorium
Abstract:
The rise of graphene in the last decade created a paradigm shift in the fundamental as well as application-oriented research of materials chemistry and condensed matter physics. Subsequently, a closely related field of topological materials prospered soon after the discovery of topological insulating states in bismuth chalcogenides. In the last few years, owing to the discovery of topological states in semimetals and metals (so called Dirac and Weyl semimetals), the area of topological materials has gained as a status of broad research area for chemists and physicists. However, the theoretical formulation of topological states is complex, they can be easily understood in terms of the behaviour of graphene. In this talk, I will introduce variety of topological states in simple compounds and try to understand their classifications based on symmetry, heaviness of the elements involved (spin orbit coupling) etc. Although these compounds are related to graphene fundamentally, they exhibit properties superior to graphene in many cases, for example extremely large mobility of electrons, high conductivity and record-breaking magnetic field induced increase in the electrical resistivity (positive magnetoresistance). Based on these excellent electronic properties, I will show that topological semimetals are also ideal candidates for hydrogen evolution catalysis.

Unlocking the Potential of Metal Fluorides for Electrochemical Energy Storage

Date & Time : Friday 15th February 2019 at 11:00 AM

Venue : SSCU Auditorium

Abstract:

Fluorine has outstanding potential as an electrode due to its high electronegativity and comparably lightweight. Employing fluorine in elemental form as a component of electrode material (in contrast to Li) is difficult, however, due to its high chemical reactivity and gaseous state. Instead, the fluoride anion (F-) may be utilized as an electrochemically stable transport ion between two electrodes. By choosing an appropriate metal/metal fluoride system combined with suitable fluoride transporting electrolyte, novel electrochemical cells can be built. Indeed, primary electrochemical cells based on fluoride transfer were realized four decades back [1], but largely overlooked until the demonstration of rechargeable fluoride ion batteries (FIBs) [2]. Since the demonstration of rechargeable FIBs, we are working on various aspects related to FIBs with the aim of developing sustainable fluoride ion batteries [3-6]. So far rechargeable FIBs have been demonstrated only at an elevated temperature like 150 °C and above. Recently, for the first time, we have demonstrated room-temperature (RT) rechargeable fluoride-ion batteries using BaSnF4 as fluoride transporting solid electrolyte [7]. BaSnF4 exhibits high ionic conductivity of 3.5×10-4 S cm-1 at RT but limited by low electrochemical stability window. In contrast tysonite-type, La0.9B0.1F2.9 electrolyte shows a large electrochemical stability window, but it has the drawback of lower ionic conductivity at RT (0.4×10−6 S cm−1). To overcome these limitations of the low electrolyte stability of BaSnF4 and low ionic conductivity of La0.9B0.1F2.9, we developed an interlayer electrolyte. Pressing a thin layer of La0.9Ba0.1F2.9 together with BaSnF4 enhanced the total conductivity of the pellet (compared to pure La0.9Ba0.1F2.9) while it physically isolated the less stable and highly conductive electrolyte (BaSnF4) from the anode (Ce). This approach allowed the demonstration of relatively high voltage FIBs at RT which otherwise inoperable either with BaSnF4 or La0.9Ba0.1F2.9 electrolyte alone [8]. Apart from applications in FIBs, transition metal fluorides could be used as high capacity cathode materials for lithium-ion batteries (LIBs), due to their ability to reversibly react with Li at relatively high potentials. However, metal fluorides are electrical insulators, exhibiting slow reaction kinetics. Consequently, efficient synthesis of metal fluoride-carbon nanocomposites is crucial to get adequate electrochemical performance. We have developed a new and facile one-step method for the chemical synthesis of novel carbon-metal fluoride nanocomposites and established their feasibility as cathode materials for LIBs [9-10]. For sodiumion batteries (SIBs) we propose weberite-type sodium metal fluorides (SMF), a new class of high voltage and high energy density materials which are so far unexplored as cathode materials for SIBs [11]. Weberite-type SMF is the only class of compounds that can offer high energy density than the state-of-the-art LIB cathodes. More than 70 compounds with Na2MM’F7 composition adopts the weberite-type structure, which demonstrates the high stability of the structure. We have modeled 22 known and 10 new compounds. Apart from the high energy density, the weberite-type structure shows low Na diffusion barriers with pseudo-3D diffusion paths. The high energy density combined with low diffusion barriers for Na makes this type of compounds promising as cathode materials for SIBs. Also, we found few lithium metal fluorides serve as excellent solid Li+ conducting electrolytes for solid-state lithium batteries, overcoming the short comes of ceramic and sulphide based solid electrolytes [12]. Overall, the presentation will highlight the potential of metal fluorides in electrochemical energy storage systems.

Among various diseases, cancer has become a big threat to human beings globally. Cancer is the second most common disease in India responsible for maximum
mortality of about 0.3 million deaths per year. This is owing to the poor availability of prevention, diagnosis, and treatment of the disease. Although
conventional chemotherapy has been successful to some extent, the main drawbacks of chemotherapy are its poor bioavailability, high-dose requirements, adverse
side effects, low therapeutic indices, development of multiple drug resistance, and non-specific targeting[1]. The main aim in the development of drug delivery
vehicles is to successfully address these delivery-related problems and carry drugs to the desired sites of therapeutic action while reducing adverse side
effects[2]. Functional nucleic acids, which can target cancer cells and realize stimuli-responsive drug delivery in the tumor microenvironment, have been widely
applied for anticancer chemotherapy[3]. At present, high cost, unsatisfactory biostability, and complicated fabrication process are the main limits for the
development of DNA-based drug-delivery nanocarriers. In this talk, I will discuss about newly developed DNA-based drug carrier, which can selectively target
tumor cells and deliver the drugs efficiently. The material exhibits a high biostability, making it a safe and ideal nanomaterial for in vivo application[4].